1. Field of the Invention
The present invention relates to a chip inductor and a manufacturing method therefor. More particularly, the present invention relates to a chip inductor manufactured by providing electrode layers having specific patterns and insulating layers on a ceramic mother board, followed by dividing the mother board, and to a method for manufacturing the chip inductor.
2. Description of the Related Art
Conventionally, multilayer chip inductors are manufactured by providing electrode layers having specific patterns and insulating layers on a ceramic (mainly alumina) mother board, and then by dividing the mother board along the break grooves formed thereon. However, when the division is performed along the break grooves formed on the mother board, the division surface often deviates from the grooves. This results in reduced dimensional precision, which is accentuated as the chip inductors are miniaturized. In the worst case, some of the electrode layers are exposed to the outside. Furthermore, since a wider margin must be provided for the division, the space for forming the internal electrode layers is substantially decreased, which causes the L value to be substantially decreased.
On the other hand, another conventional method for manufacturing an inductor is described in Japanese Unexamined Patent Application Publication No. 11-176685, in which a conductive film is formed on the side surfaces of a ferrite core, and the conductive film is subjected to laser machining to form a spiral conductive pattern.
In the course of developing the present invention, various attempts were made to use the method disclosed in the above-described Publication for manufacturing the conventional chip inductor. In that method, glass was used to define the uppermost insulating layer, and the insulating layer was irradiated with a laser beam to form break grooves. However, glass was difficult to cut with the laser beam, and therefore, it was not possible to divide the board.
To overcome the above-described problems with the prior art, preferred embodiments of the present invention provide a chip inductor manufactured from a mother board which is accurately divided along break grooves, and requires only a narrow margin for the division, such that a large L value is achieved, as well as to provide a method for manufacturing the chip inductor.
Furthermore, preferred embodiments of the present invention provide a chip inductor that eliminates and prevents degradation of the Q value at a high frequency.
A chip inductor according to a preferred embodiment of the present invention includes electrode layers with specific patterns and insulating layers on a ceramic board, wherein a pigment including an inorganic oxide is added to an uppermost insulating layer within the range of about 2% to about 20% by weight.
The chip inductor having the unique configuration described above is manufactured preferably by providing electrode layers having specific patterns and insulating layers on a ceramic mother board, adding a pigment including an inorganic oxide to an uppermost insulating layer within the range of about 2% to about 20% by weight, irradiating the uppermost insulating layer with a laser beam to form lattice-shape grooves, and then dividing the mother board along the grooves.
When a pigment including an inorganic oxide is added to an insulating layer (made of glass, a polyimide, or other suitable material), the pigment absorbs the energy of a laser beam such that break grooves are effectively formed. Grooves having a width as narrow as about 30 xcexcm are formed by the laser beam irradiation. When a mother board is divided along these grooves, deviation of the division surface from the grooves is avoided. Furthermore, the margin for the division is substantially narrower, and therefore, the area for providing the electrode layers is greatly increased, with the result that a larger L (inductance) value is achieved at a high frequency.
As the inorganic oxide to be added to the insulating layer, oxides of Co, Al, Fe, Mn, or other suitable materials are used. More particularly, when a Co oxide and/or an Al oxide is used, deterioration of the Q value at a high frequency is prevented.
Furthermore, according to a preferred embodiment of a manufacturing method of the present invention, in addition to the formation of grooves for breaking on the above-described uppermost insulating layer, grooves may be formed on the bottom surface of the mother board which correspond to the grooves formed on the above-described uppermost insulating layer. The generation of burrs is prevented at the time of dividing the mother board, and the outer dimensional precision of the chips is further improved.
It is noted that the laser ray absorption effect does not occur when the amount of the inorganic oxide added to the insulating layer is less than about 2% by weight, and that the Q value and the strength of the insulating layer (deterioration of sintering characteristics) substantially deteriorates if the amount of inorganic oxide exceeds about 20% by weight.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached figures.